*{
  margin:0;
  padding:0;
  box-sizing: border-box;
}

body{
  font-family: sans-serif;
  padding:20px;
}

.flashcards{
  display: grid;
  grid-template-columns: 1fr 1fr 1fr;
  gap:20px;
}

.flashcards div{
  border:1px solid #e7e7e7;
  background-color: #f7f7f7;
  border-radius: 7px;
  aspect-ratio: 2 / 1;
  display: flex;
  align-items: center;
  justify-content: center;
  text-align: center;
  padding:20px;
  cursor: pointer;
}

div.selected{
  border:1px solid #e03131;
  background-color: #e03131;
  color:#fff;
  font-weight: bold;
}